Time Machine back up- what to exclude..?

I'd like to make the most of my external HD space when I use TM to back up. Can anyone tell me what files to exclude? I exclude OS and Applications right now....I'm more concerned in backing up documents, NEW music and NEW photos only. The rest is not needed.
Thank you for your attention to this.
Ben

Your post was moved to the correct forum. It does not belong in "The Lounge".

I generally advise folks not to exclude anything. You never know when your Time Machine backup has to be used to recover your entire hard drive. If you exclude things that later on are needed, they will be lost. And as inexpensive as large external hard drives are, there really is no reason to worry about saving space. Of course that's entirely up to you, but it's something to consider before you decide.